Polyblends are known in the art as tough engineering plastics having high modulus and great utility for fabricated parts for appliances and automotive parts. ABS polyblends generally comprise a rigid matrix copolymer phase of styrene and acrylonitrile monomers having dispersed therein a graft copolymer of a diene rubber substrate grafted with the styrene/acrylonitrile copolymer. It is known that the graft copolymer is incompatible with the matrix phase and has a different refractive index, hence, the polyblend has a high level of haze providing opaque and translucent polyblends which are generally pigmented as fabricated parts.
There has now been developed a great need for highly transparent polyblends that can be fabricated into transparent parts yet provide the same high level of toughness and modulus typical of ABS polyblends.
The prior art discloses several transparent graft copolymer systems but not for the ABS polyblend types. The transparent graft copolymers disclosed by U.S. Pat. Nos. 2,857,360, 3,177,268, 3,644,584, 3,586,737, 3,670,052 and 3,775,518 teach graft copolymer systems using diene rubber substrate grafted with high levels of acrylate and/or nitrile monomers to provide a graft copolymer with a superstrate refractive index closer to the low refractive index of the diene rubber substrate, hence, providing a transparent graft copolymer for blending with polyvinyl chloride polymethyl methacrylate providing transparent polyblends.
It has now been discovered that diene rubber substrates grafted with styrene/acrylonitrile copolymer superstrates only can be blended with particular matrix styrene terpolymers to provide transparent polyblends having the toughness and modulus of ABS polyblends.